Method of making a camshaft

Abstract

A method of forming a camshaft tube having a plurality of thinner wall sections adjacent to thicker wall sections. The diameter of a hollow tube is mechanically reduced with a retractable mandrel inserted in the hollow tube. The retractable mandrel has a first portion having a larger diameter than an adjacent second portion. To form a thinner wall section, the larger diameter first portion is positioned under a reducing tool. To form a thicker portion, the smaller diameter second portion is positioned under a reducing tool.

Having described the invention, what is claimed is: 
     
       1. A method of forming a camshaft tube comprising the steps of: providing a hollow tube;   providing a retractable mandrel, the retractable mandrel having a first portion and a second portion adjacent the first portion, the diameter of the first portion being larger than the diameter of the second portion;   inserting the retractable mandrel into the hollow tube;   mechanically reducing a first section of the hollow tube, the first portion of the retractable mandrel being positioned under the section of the hollow tube being reduced;   positioning the second portion of the retractable mandrel under a second section of the hollow tube; and   mechanically reducing the second section of the hollow tube, the second portion of the retractable mandrel being positioned under the section of the hollow tube being reduced.   
     
     
       2. The method according to claim 1, further comprising: repeating the steps of mechanically reducing a first section of the hollow tube, the first portion of the retractable mandrel being positioned under the section of the hollow tube being reduced; positioning the second portion of the retractable mandrel under a second section of the hollow tube; and mechanically reducing the second section of the hollow tube, the second portion of the retractable mandrel being positioned under the section of the hollow tube being reduced, thereby forming a plurality of first sections and second sections, the inner diameter of a first section being larger than the inner diameter of a second section.   
     
     
       3. The method according to claim 1, further comprising: providing a swaging tool; and   using the swaging tool to mechanically reduce the hollow tube.   
     
     
       4. A method of forming a camshaft tube comprising the steps of: providing a hollow tube;   providing an axially extending retractable mandrel, the retractable mandrel having a first portion and a second portion adjacent the first portion, the diameter of the first portion being larger than the diameter of the second portion, the second portion being an end of the retractable mandrel;   inserting the retractable mandrel into the hollow tube;   positioning the retractable mandrel whereby the first portion of the retractable mandrel is positioned under a first section of the hollow tube;   providing a swaging tool;   mechanically reducing the first section of the hollow tube by pushing the hollow tube through the swaging tool, the retractable mandrel also being moved to keep the first portion of the retractable mandrel positioned under the section of the hollow tube being reduced;   retracting the retractable mandrel to position the second portion of the retractable mandrel under a second section of the hollow tube;   mechanically reducing the second section of the hollow tube;   repeating the steps of positioning the retractable mandrel whereby the first portion of the retractable mandrel is positioned under a first section of the hollow tube; mechanically reducing the first section of the hollow tube by pushing the hollow tube through the swaging tool, the retractable mandrel also being moved to keep the first portion of the retractable mandrel positioned under the section of the hollow tube being reduced; retracting the retractable mandrel to position the second portion of the retractable mandrel under a second section of the hollow tube; and mechanically reducing the second section of the hollow tube by pushing the hollow tube through the swaging tool, thereby forming a plurality of first sections and second sections, the inner diameter of a first section being larger than the inner diameter of a second section.   
     
     
       5. A method of making a camshaft comprising the steps of: providing a hollow tube;   providing a retractable mandrel, the retractable mandrel having a first portion and a second portion adjacent the first portion, the diameter of the first portion being larger than the diameter of the second portion;   inserting the retractable mandrel into the hollow tube;   mechanically reducing a first section of the hollow tube, the first portion of the retractable mandrel being positioned under the section of the hollow tube being reduced;   positioning the second portion of the retractable mandrel under a second section of the hollow tube;   mechanically reducing the second section of the hollow tube, the second portion of the retractable mandrel being positioned under the section of the hollow tube being reduced;   repeating the steps of mechanically reducing a first section of the hollow tube, the first portion of the retractable mandrel being positioned under the section of the hollow tube being reduced; positioning the second portion of the retractable mandrel under a second section of the hollow tube; and mechanically reducing the second section of the hollow tube, the second portion of the retractable mandrel being positioned under the section of the hollow tube being reduced, thereby forming a plurality of first sections and second sections, the inner diameter of a first section being larger than the inner diameter of a second section, the second sections forming reduced diameter zones;   providing a plurality of cam elements, each cam element including an axial opening;   inserting the hollow tube into the cam elements, each cam element being positioned about a reduced diameter zone;   expanding the reduced diameter zones of the hollow tube into mechanical interference engagement with the cam elements.   
     
     
       6. The method of claim 5 wherein the areas of the hollow tube adjacent the reduced diameter zones define larger diameter zones and the larger diameter zones do not expand during the step of expanding the reduced diameter zones. 
     
     
       7. The method of claim 5, further comprising: providing an expander tool having a diameter larger than the inner diameter of the thicker wall zones and smaller than the inner diameter of the thinner wall zones; and   using the expander tool to expanding the thicker wall zones of the hollow tube into mechanical interference engagement with the cam elements by inserting the expander tool into the hollow tube.